The Role of Dopamine, Reward Learning and Prefrontal Activity in Expectation-induced Mood Enhancement

• Status: Recruiting
• Trial end date: 2024-06-30
• Target enrollment: 0
• Participant gender: All

Summary

Although placebo effects on depressive symptoms are well documented, the underlying mechanisms and moderating factors of expectation effects on mood and depression are poorly understood. Various studies show reduced reward processing in clinical and subclinical depression, presumably due to abnormalities in the dopamine (DA) system. Here, the investigators will test whether expectation-induced mood enhancement is mediated by endogenous DA activity and reward learning, and moderated by individual differences in depression-related personality traits. Healthy participants (N=296) will be tested for potentially relevant personality traits and given an inactive substance (placebo) or a DA D2-receptor antagonist sulpiride (400 mg) in combination with a low vs. high expectation manipulation (fully crossed 2x2 placebo design) before performing a probabilistic reinforcement learning task, an effort expenditure task, and undergo a depressed mood induction procedure. Further, EEG indices will be assessed throughout the tasks.

The investigators expect that positive expectation improves participants' reinforcement learning, increases participants' willingness to make effort in order to obtain reward, and leads to less depressive symptoms as indicated by mood ratings upon depressive mood induction. If the overall effect of positive expectations is mediated by DA, high-dose sulpiride should block expectation-induced effects, i.e., the anticipated enhanced reinforcement learning and effort expenditure as well as mood improvement in the high vs. low expectation group.

• Phase: N/A
• Accepts Healthy Volunteers?: Accepts Healthy Volunteers

Details

• Lead Sponsor: Philipps University Marburg Medical Center
• Treatments: Sulpiride

Criteria

Inclusion Criteria:

• Right-handed

• Aged 18-60 years

• German native speaker

• Informed consent

• Normal or corrected sight

Exclusion Criteria:

• Current pregnancy

• Current or history of general medical, neurological or psychological disorders, which preclude sulpiride intake

• Self-reported presence of mental disorders

• Liver, kidney, and bowel disorders

• Regular smoking

• Reported alcohol abuse

• Illegal drug intake

• Regular drug intake by prescription in the past three months

• Dreadlocks

• BMI < 19 or > 30

• Unremovable metal objects around the head

• Previous knowledge of Japanese characters

• Excessive caffeine intake (> 8 cups per day)